This invention is concerned with lining of sewer pipes and the like and is more particularly concerned with providing a folded liner that can be pulled through a pipe for later expansion by conventional techniques.
Because of the expense of repairing and/or replacing defective sewer pipes and the like, an industry practice has developed in which the pipes are lined with a plastic liner, thereby to provide a new flow path within the defective pipe. In order to facilitate the pulling of the liner through the pipe, techniques have been developed for folding a flattened thermoplastic liner before it is introduced to the pipe so that the cross-dimensions of the liner, when folded, are substantially less than the cross-dimensions of the pipe. However, providing a folded liner efficiently, reliably, and economically has been a problem. The present invention is a solution to that problem.
In a broad sense, the invention concerns a machine and method of providing tubing that is folded about a longitudinal axis whereby the cross-section of the tubing assumes a configuration comprising overlapping loops. More particularly, the loops are formed as the tubing is fed in a first direction, and then the tubing is redirected and the orientation of the loops is changed.
In a preferred embodiment, a machine of the invention comprises an upper section and a lower section, which are preferably separable. As a heated flexible liner of flattened cross-section is fed into and through the upper section to the lower section, it is broadly indented at one side thereof and is then more acutely indented to fold the liner so that the cross-section assumes a configuration in which a pair of outer loops are disposed at opposite sides of a central loop along a substantially horizontal direction.
As the folded liner is fed through the lower section, it is redirected so that it is fed substantially horizontally, with the cross-sectional loops stacked substantially vertically. The liner fed from the lower section is cooled to reduce its flexibility, so that the cross-sectional configuration is maintained as the liner is drawn into and through a pipe, in a conventional manner.
In a preferred embodiment of the invention, portions of the upper and lower sections can be displaced, and can also be removed, to facilitate initial entry of the liner into the upper section, and also to facilitate withdrawal of the machine from the liner after the liner has been drawn to a desired position in the pipe. After the liner has been installed in the pipe, and the machine withdrawn, a trailing portion of the liner can be cut and the liner can be heated and expanded by conventional techniques, thereby unfolding the liner and providing a round cross-section.